The present invention relates to MEMS switches/relays and more specifically to systems for extending the life of MEMS switches/relays.
Micro-machined (MEMS) relays are known in the art and can be used for creating a near ideal switch that has a plurality of states. MEMS relays 100 include a cantilevered beam 101 that bends as the result of electrostatic forces due to the presence of a voltage 105 at the gate 102 of the MEMS relay 100 as shown in FIG. 1. Thus, when the beam bends, an electrically conductive portion 106 of the underside of the beam completes a circuit path between a first portion of the signal path 103 and the second portion of the signal path 104. Although, MEMS relays produce near ideal switches, because of their small size, MEMS relays are sensitive to charge. During a state-change, as the result of parasitic capacitances, a differential voltage between the input and the output of the MEMS relays can result in large current flowing through the MEMS switch. As the beam of the MEMS relay completes the signal path, the resulting current can cause pitting of the beam and potentially weld the beam in a closed position. Thus, the imbalance in charge at the input and output of the MEMS relay will greatly reduce the number of potential cycles of use and will eventually lead to the relay's failure. Similarly, three terminal MEMS switches suffer from the same problem.
In addition to parasitic capacitance discharge, the life of a MEMS switch/relay is also greatly reduced as the result of “hot-switching.” Hot-switching occurs when a signal is driven along the signal path while the MEMS switch/relay is changing states. As the beam of the MEMS switch/relay deflects and comes partially into contact with the signal path sections, the driven signal can cause a large current surge and arching. This surge in current can damage the beam of the MEMS switch/relay and cause switch failure.